This invention relates to connectors, especially coupling members for substrates such as pipes.
The pipes used in central heating systems are generally coupled by traditional methods such as brazing. Similar methods are also employed in, for example, the coupling of larger pipes such as those used for desert irrigation. Apart from obvious disadvantages, such as the time required to make each connection, the need for skilled operators and the need to provide suitable equipment at the area of operation, these methods have the further disadvantage of placing a limitation on the choice of material used for the pipes. For example, brazing cannot be satisfactory employed with aluminium pipes.
It has been proposed to make coupling members from heat-recoverable materials. For example, U.S. Pat. No. 3,315,986 proposes the use of heat-shrinkable plastics materials in the coupling of hose pipes and British Pat. No. 1,327,441 proposes the use of heat-shrinkable, internally toothed, metal coupling members for the connection of hydraulic pipes. However, unless special measures are taken, the connections obtained with heat-shrinkable plastics materials are, in general, unable to withstand high internal pressures and cannot reliably provide a long term seal against the egress of, for example, liquids flowing through the pipes, and the alloys used in the heat-shrinkable metal coupling members are too expensive to warrant their use in anything but specialised applications.